Table 15.

Details on modalities and reliability for monitoring the respiratory system

Modality	Reliability in cats	Comments
Respiratory rate	±	Respiratory rate is not a good indicator of efficiency of air movement into and out of the lungs. Respiratory rate does not indicate that patient is inspiring or absorbing adequate oxygen
Mucous membrane color	−	Human eyes cannot detect meaningful changes in oxygenation until patient becomes cyanotic (SpO2 = ~70–80%)
Tidal volume	+	Difficult to determine breath volume by visually assessing reservoir bag or chest movement due to small patient size
Pulse oximeter without waveform	+	Without a waveform it is difficult to assess signal quality. Does not indicate patient is breathing
Pulse oximeter with waveform	++	A steady waveform is indicative of good signal quality; many factors affect signal quality including exposure to ambient light, tissue compression, drying of tissue (See Figure 23 for SpO2 troubleshooting tips). Does not indicate patient is breathing
Capnometer (no waveform)	+	Difficult to assess accuracy of monitor without waveform
Capnograph with waveform	+++	Waveform analysis provides invaluable insight into respiratory function and equipment malfunction (eg, stuck unidirectional valves in a circle system)
Arterial blood gases	++++	Gold standard for evaluating ventilation. Obtaining sample can be difficult; requires specialized equipment. Rarely used in clinical practice

− = Not reliable; + = poor reliability; ++++ = very reliable; SpO2 = oxygen saturation of hemoglobin in arterial blood